NEW YORK -- Packet-Optical Transport Evolution -- AT&T Inc. (NYSE: T) has been deploying 40-Gbit/s lines for years, but it hasn't been easy. For one thing, the stuff didn't always work properly.

The point came up early today in Light Reading's Packet-Optical Transport Evolution conference. Speaking during a 100-Gbit/s workshop that preceded the conference sessions, AT&T executive director Margaret Chiosi said she's hoping 100 Gbit/s can avoid the problems that emerged with 40-Gbit/s equipment -- one of those being faulty boards.

"We must have changed out all our cards two times: Class A changes," Chiosi said. "Decades ago, Class A changes would be career-ending. If you had one, you were out of a job. Two, forget it."

AT&T eventually figured out that the problem was industry-pervasive -- other operators kept swapping out equipment, too, and didn't realize the problem was systemic. AT&T traced it down to a single chip, one that was ubiquitous in 40-Gbit/s gear. (Chiosi didn't specify the device any further.)

Obviously, avoiding that kind of thing at 100 Gbit/s would be nice. Vendors are so anxious to differentiate themselves, maybe quality could be a factor, Chiosi quipped.

Another well established problem with 40 Gbit/s was the lack of a standard implementation -- vendors offering different modulation schemes, for instance. In that race to provide differentiation, vendors also kept churning out more cards. AT&T is now on its third or fourth generation of 40-Gbit/s cards, and the continual turnover might be part of the reason vendors have trouble making money, Chiosi contended.

"You put out one version, and it takes us 18 months or two years to certify it and get it out the door -- and once we get it out the door, there's another version," she said.

This problem is already being addressed, at least, with the Optical Internetworking Forum (OIF) developing a 100-Gbit/s framework that can serve as a unified front for the industry.

— Craig Matsumoto, West Coast Editor, Light Reading